Fluid Mechanics Chapter 1 and 2

no-slip condition

A fluid in direct contact with a solid "sticks" to the surface, and there is no slip.

forced flow

A fluid is forced to flow over a surface or in a pipe by external means such as a pump or a fan.

system

A quantity of matter or a region in space chosen for study

total energy

All energy, potential and kinetic, within a specific system.

ideal gas equation

An equation of state for gases that can be described by the equation PV = nRT.

gas dynamics

Deals with the flow of fluids that undergo significant density changes, such as the flow of gases through nozzles at high speeds.

aerodynamics

Deals with the flow of gases (especially air) over bodies such as aircraft, rockets, and automobiles at high or low speeds.

viscous flows

Flows in which the frictional effects are significant.

natural flow

Fluid motion is due to natural means such as the buoyancy effect, which manifests itself as the rise of warmer (and thus lighter) fluid and the fall of cooler (and thus denser) fluid.

Newtonian Fluid

Fluids for which the rate of deformation is linearly proportional to the shear stress.

Inviscid flow regions

In many flows of practical interest, there are regions (typically regions not close to solid surfaces) where viscous forces are negligibly small compared to inertial or pressure forces.

sonic

Ma = 1

hypersonic

Ma greater than one

subsonic

Ma less than one

internal energy

Sum of all microscopic forms of energy

Reynolds number

The dimensionless parameter that defines the flow regime as either laminar, transitional, or turbulent

Internal flow

The flow in a pipe or duct if the fluid is completely bounded by solid surfaces

external flow

The flow of an unbounded fluid over a surface such as a plate, a wire, or a pipe.

saturation pressure

The pressure at which a pure substance changes phase at a given temperature

specific gravity/relative density

The ratio of the density of a substance to the density of some standard substance at a specified temperature.

fluid mechanics

The science that deals with the behavior of fluids at rest (fluid statics) or in motion (fluid dynamics), and the interaction of fluids with solids or other fluids at the boundaries.

State Postulate

The state of a simple compressible system is completely specified by two independent, intensive properties.

hydrodynamics

The study of the motion of fluids that can be approximated as incompressible (such as liquids, especially water, and gases at low speeds).

continuum

a continuous system without apparent holes or discontinuities

unsteady flow

a flow in which quantity of liquid flowing per second is not constant

drag force

a force that opposes the motion of an object through a fluid

intensive property

a physical property that remains the same no matter how much of a substance is present

extensive property

a property that depends on the amount of matter in a sample

open system/control volume

a selected region in space both mass and energy can cross the boundary

fluid

a substance in the liquid or gas phase deforms continuously under the influence of a shear stress

specific properties

are extensive properties on a per mass basis therefore defined as intensive properties

open channel flow

at least one free surface

solid

can resist applied shear stress by deforming stress is proportional to strain

closed system/control mass

consists of a fixed amount of mass and no mass can cross its boundary, but energy in the form of heat or work can volume does not have to be fixed

hydraulics

deals with liquid flows in pipes and open channels

incompressible

density remains nearly constant throughout

Coefficient of compressibility/bulk modulus of compressibility

describes the resistance to being compressed, with large k value a larger pressure is needed to compress the fluid

Coefficient of volume expansion

describes the variation of the density of a fluid with temperature at constant pressure

vapor pressure

equal to the saturation pressure at a given temperature.

boundary layer

exist in the flow adjacent to surfaces where the flow is brought to rest characterized by high shear with the highest velocities away from the surface the flow region adjacent to the wall in which the viscous effects are significant

transitional

flow that alternates between laminar and turbulent

stress

force per unit area

steady flow

no change of properties, velocity, temp, etc at a point in time mass flow rate in is equal to mass flow rate out

uniform

no change with location over a specified region or distance the velocity stays constant

viscosity

resistance to flow

potential energy

stored energy that results from the position of an object

transient flow

term used to describe developing flows

kinetic energy

the energy an object has due to its motion

turbulent

the highly disordered fluid motion that typically occurs at high velocities and is characterized by velocity fluctuation

laminar

the highly ordered fluid motion characterized by smooth layers of fluid

periodic

the kind of unsteady flow in which the flow oscillates about a steady mean

cavitation

the phenomenon in which the liquid's pressure drops below the vapor pressure resulting in bubbles that will collapse and generate highly destructive, extremely high pressure waves

Mach number

the ratio of an object's speed of flow to the speed of sound (Ma)

hydrology

the study of water and its effects on and in the earth and in the atmosphere

enthalpy

the sum of the internal energy of a system plus flow energy

shear stress

the tangential component of a force acting on a surface per unit area

saturation temperature

the temperature at which a pure substance changes phase at a given pressure

specific weight

weight per unit volume

flow separation

when a fluid is forced to flow over a curved surface, the boundary may no longer remain attached to the surface and separates from the surface

isolated system

when mass, heat, and work are not allowed to cross the boundaries of a system

No temperature jump condition

when two bodies at different temperatures are brought into contact, heat transfer occurs such that both bodies assume the same temperature at points of contact